Method and apparatus for removing thimbles from the stubs of an anode

Abstract

An apparatus and method for removing thimbles ( 12 ) from stubs ( 20 ) of an anode yoke which includes the step of advancing a ram ( 20 ) towards each stub with the force applied by the ram against the stub being limited to a preset maximum, and another step of advancing the rams at the same speed to push the stubs through the thimbles.

What is claimed is:  
     
       1. An apparatus for removing thimbles from stubs of an anode, the apparatus comprising: 
       a plurality of rams having independent movements; and  
       a ram control system including,  
       a first mode designed to advance each ram towards a stub and the force applied by the ram against the stub is limited to a preset maximum force, and  
       a second mode designed to advance the rams at the same speed to push the stubs through the thimbles.  
     
     
       2. The apparatus of  claim 1  further including a plurality of stops, wherein each stop is positioned to stop the movement of one of the thimbles, thereby allowing the ram to push the stub through the thimble 
     
     
       3. The apparatus of  claim 1 , wherein the ram control system is a hydraulic system. 
     
     
       4. The apparatus of  claim 3  further including a plurality of hydraulic circuits, each hydraulic circuit being operatively associated with one of the rams to drive the ram. 
     
     
       5. The apparatus of  claim 4 , wherein each hydraulic circuit includes a piston-cylinder arrangement for driving the ram associated with the hydraulic circuit. 
     
     
       6. The apparatus of  claim 5 , wherein each hydraulic circuit includes a pump operatively connected to the piston-cylinder arrangement of the circuit. 
     
     
       7. The apparatus of  claim 6 , wherein the pumps have the same displacement and are arranged in tandem with a motor to synchronize the movement of the piston-cylinder arrangements. 
     
     
       8. The apparatus of  claim 5 , where n each hydraulic circuit includes a pressure reducing valve, wherein the pressure reducing valve limits the pressure of the circuit to a preset maximum pressure when the ram control system is in the first mode, thereby limiting the force applied by the ram against the stub is limited to the preset maximum force. 
     
     
       9. The apparatus of  claim 8 , wherein each hydraulic circuit includes a pressure sensor, wherein the ram control system enters the second mode when the pressure sensor of each hydraulic circuit indicates that the pressure of the hydraulic circuit has reached the preset maximum pressure. 
     
     
       10. The apparatus of  claim 9 , wherein the pressure of each hydraulic circuit is not limited to the preset maximum pressure when the ram control system is in the second mode. 
     
     
       11. A method for removing thimbles from stubs of an anode, the method comprising: 
       advancing a ram towards each stub, while limiting the force applied by the ram against the stub to a preset maximum force; and  
       advancing the rams at the same speed to push the stubs through the thimbles, while not limiting the force applied by each ram to the preset maximum force.  
     
     
       12. The method of  claim 11 , wherein starting advancing the rams at the same speed after the forces applied by the rams against the stubs reach the preset maximum forces. 
     
     
       13. The method of  claim 11  further including holding at least one of the thimbles stationary while advancing the rams at the same speed to push the stubs through the thimbles. 
     
     
       14. The method of  claim 11 , wherein advancing a ram towards each stub includes advancing the ram towards the stub using a hydraulic circuit that includes a piston-cylinder arrangement and a pump operatively connected to the piston-cylinder arrangement. 
     
     
       15. The method of  claim 14 , wherein limiting the force applied by the ram against the end to the preset maximum force includes limiting the pressure of the hydraulic circuit to a preset maximum pressure. 
     
     
       16. The method of  claim 15 , wherein advancing the rams at the same speed includes providing the pumps with the same displacement and driving the pumps in tandem.